Undo covers every change and says what it reversed #23

Undo should cover every change and say what it reversed: renaming a board is silently not undoable, and pressing Undo tells you nothing about what it just did.

Two real defects in src/db.ts and src/pages/board.ts:

• renameBoard is the only mutation that never calls logAction. Rename a board, press Undo, and the name stays while some earlier change — a card you moved a minute ago — is reversed instead. On a board several people share, that is someone else's work disappearing with no trace.
• undo(boardId) returns only true/false. The page shows nothing at all on success, so nobody can tell what came back. Undo is board-wide, not per-person: it reverses the board's last change, whoever made it, and the button gives no clue that this is what it will do.

Done looks like

• [ ] renameBoard logs its previous row like every other mutation — restoreBoards?: Board[] in Payload, restored with INSERT OR REPLACE in undo — inside the same transaction the other mutations use after #15.
• [ ] Every action row carries a short human label written where the change happens: renamed the board, moved "Ship it", deleted the column "Doing", added "Ship it". It is stored in the payload, so old rows without one still undo cleanly.
• [ ] undo(boardId) returns the label of what it reversed (string | null), POST /b/<id>/undo returns it in its JSON for the board script and still redirects for the no-JS path, and the board announces Undid: moved "Ship it" in the existing #toast — as a neutral message, not the red error styling, and still role="status" so a screen reader hears it.
• [ ] The Undo button says what it would undo (title and aria-label: Undo: moved "Ship it"), read on the server with one indexed SELECT payload … ORDER BY id DESC LIMIT 1, so the board-wide nature of Undo is visible before it is pressed.
• [ ] With nothing left to undo the button is rendered disabled with a plain "Nothing to undo", instead of posting and getting a 404.
• [ ] Tests in src/server.test.ts, each failing on main: renaming a board and undoing restores the previous name; a label round-trips through the action log into both the JSON response and the rendered button; undo on a fresh board answers {ok:false} without throwing and renders the disabled button; a card titled <b>"x"</b> appears escaped in both the button's title attribute and the JSON-driven toast.

Files I expect to change

• src/db.ts — the rename's action row, the label in Payload, undo's return.
• src/routes.ts — the undo response carrying the label.
• src/pages/board.ts — the button's label and disabled state.
• static/board.<newhash>.js — the success toast, and BOARD_JS updated to match.
• src/server.test.ts.

Risks

• Blocked by #15: that change rewrites every mutation in src/db.ts into transactions, and this one adds a row to the same places. Land it after, and follow whatever shape #15 leaves behind.
• Labels are user text. Escape them where every other output is escaped, including inside the title attribute, and cap their length — the payload's growth is bounded by #16, not here.
• Do not turn Undo into per-person undo in this change. Making it honest about being board-wide is the fix; whose change it was becomes answerable once identity (#10) lands.

Suggested: scout.

Parked by the crew: the check failed and the decider saw no point in another try (pull #32 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Split and closed, not abandoned. This asked for four things in one run — a missing logAction in renameBoard, a label on every action row, a label on the Undo button, and a toast wired into static/board.*.js — and pull #32 got the first three right and failed the check on the fourth (src/live-refresh.test.ts, two cases), which took the whole pull down with it.

What replaces it, both open and true to main at e888c44:

• #42 — Renaming a board can be undone: renameBoard logs the row it overwrote. The one real data defect, on its own: today renaming a board and pressing Undo reverses someone else's earlier change instead.
• #43 — Undo says what it reversed: a label on the action row and on the Undo button. The server and the server-rendered page only, with static/board.*.js explicitly out of scope; it waits for #42 because both rewrite every mutation in src/db.ts.

The toast — telling a person in the open page what Undo just did, without a reload — is deliberately not filed yet: pull #36 is rewriting static/board.*.js for #12, and a third small issue can add it once that lands and there is a file to edit that will still exist.